Circuit breakers for low voltages are generally known and have a movable and a fixed contact for opening and closing, which have contact pieces facing each other. The contact pieces are arranged on the free end of a contact lever, which is rotationally mounted on or in a switch shaft. The contact lever extends transversely to the longitudinal axis of the switch shaft and protrudes from the switch shaft with its free end. On the same side of the rotational axle opposite the contact piece in the outer contour of the contact lever is located a recess for suspension of a pin, which is aligned parallel to the switch shaft. Springs engage on both ends of the pin, which apply a torque to the contact lever in the closing direction. In the case of a closed circuit breaker the contact pieces of the two contacts are pressed against each other by means of the spring force. The contact lever is generally embodied as a double lever. Leaf and wound wire springs are used as springs. These can be embodied as tension, compression or torsional springs.
In the event of a short circuit the contacts open after the exceeding of a prescribed current threshold. An electric arc here occurs between the contact pieces. This has the desirable property that it limits the current. The plasma and hot gas generated by the electric arc, whose temperature is far higher than 1000 degrees Celsius, has the disadvantage that it can damage parts of the rotor. In the case of compact circuit breakers this relates in particular to the springs, in light of its small structural volume.
In order to compensate for deformation of the springs, they are, for example overdimensioned, as a result of which due to their greater mass they have a greater resistance to heat. This again however leads to a greater installation volume in the rotor-housing, and a stronger actuation mechanism is required. It is also known to route the springs outwards by means of deflection parts and to shield them there by way of a cover. The number of individual parts of the circuit breaker and the assembly effort are, however, increased thereby. It is also known to cover the rotor body with the springs radially by means of a cylinder.